Add MultiRippleView and its controller to support UMO touch ripple

effects.

The current RippleView is designed for a single ripple effect. For UMO
touch ripple, multiple touch ripple effects should be supported, thus
adding a new MultiRippleView. RippleView may be refactored such that it
takes in RippleAnimation later.

Design doc: go/surface-effects-umo
Bug: 237282226
Test: MultiRippleControllerTest, RippleAnimationTest

Change-Id: Ic199a5552b0c40e5c09c12f06c280ff054f462cb